I. Field of the Invention
This invention relates to the purging and non-destructive testing of dynamoelectric equipment typically utilizing a branched fluid cooling system, as well as to transformers. Specifically, the invention apparatus consists of an automatic and adjustable self contained unit which forces fluids and contaminants from without conductive cooling tube-equipped stators/transformers with cycles of compressed air, in periodic escalating pressures, holds the pressures in order to test integrity, and ultimately switches to high vacuum for final evacuation, test and preparation for subsequent conductivity (megger) testing. Integral, automatic and highly flexible, the invention finds its greatest application in rotating electrical equipment stator cooling systems.
II. Discussion of the Relevant Art
Large dynamoelectric equipment, such as generators, typically use branched fluid cooling systems. Parts of this equipment, such as the stator coils, are internally cooled by the circulation of a liquid such as water or oil. Generally, the operational atmosphere of these parts is pressurized hydrogen. The pressure of the coolant in the coil is less, by design, than the pressure of the hydrogen ambient pressure. Theoretically, a leak in a coil carrying coolant should allow the entry of hydrogen to the coil rather than venting of fluid to the atmosphere. Unfortunately, a bubble of such hydrogen gas within the coil is sufficient to at least partially block passage of the fluid coolant, thus creating hot spots which deteriorate stator insulation, diminish conductivity and ultimately cause shut-down of the equipment.
Periodic tests of conductivity of the stators are useful in prevention of accidents and unscheduled shut-downs of the equipment. The results of such tests depend, to some extent, on the degree to which all fluids and contaminants are first removed from the cooling lines. Periodic test protocols are also useful for determining advanced warning of breakdowns in the integrity of the lines, however minute. I have made this invention, specifically, to perform both services on the aforementioned dynamoelectric equipment.